Water-soluble lubricating agent for plastic working, metal material for plastic working, and worked metal article

ABSTRACT

Provided is a water-soluble rubricating agent for plastic working being capable of forming a lubricating film having lubricity and seizure resistance equal to or greater than a phosphorus-containing chemical conversion treatment film, having excellent corrosion resistance, and also having good film adhesion, without including phosphorus in the film. This water-soluble non-phosphorus lubricating agent for plastic working includes an inorganic solid lubricant as component A, a wax as component B, and a water-soluble inorganic metal salt as component C, wherein the mass ratio (component A/component B) of solid content for component A to solid content for component B is 0.1 to 5, and the mass percentage (component C/(component A+component B+component C)) of solid content for component C to total solid content for components A, B and C is 1 to 30%.

TECHNICAL FIELD

The present invention relates to a water-soluble lubricating agent for plastic working, a metal material for plastic working, and a worked metal article. More particularly, the present invention relates to a water-soluble lubricating agent for plastic working being capable of forming a lubricating film having excellent film characteristics such as lubricity, seizure resistance, corrosion resistance, adhesion, and the like without including phosphorus in the film, and a metal material for plastic working and a worked metal article including such a lubricating film. The metal material of the present invention is suitably used to manufacture worked metal articles such as, for example, machine parts such as bolts, nuts, springs and the like, and wire drawing products such as steel cords, bead wires, PC (prestressed concrete) steel wires and the like, which are obtained by plastic working such as drawing, pressing, forging, heading and the like.

BACKGROUND ART

A metal material for plastic working is subjected to various plastic workings such as drawing, wire drawing, heading and forging according to its applications. During plastic working, a high pressure is applied between a working tool (a die, plug, punch or the like) and a material to be worked (a meal material), and seizure is likely to occur with accompanying sliding between each other. Therefore, in order to decrease the friction on the surface of the metal material and prevent seizure, a lubricating film is usually formed on the surface of the metal material.

As the lubricating film, typically, a composite film (hereinafter it may be referred to as “chemical conversion treatment film”) composed of a phosphate film and a soap layer can be given. This chemical conversion treatment film is obtained in the following manner, for example. First, a phosphate film is formed on a metal material by performing a phosphate treatment. Then, by performing a reactive soap lubricating treatment, the phosphate film is reacted with sodium stearate that is a main component of the soap to form a soap layer including zinc stearate (metal soap) having good adhesion and sodium stearate (hot water bath soap), so that the chemical conversion treatment film can be obtained. This chemical conversion treatment film has excellent lubricity and excellent seizure resistance, and also good corrosion resistance. Therefore, the metal material provided with such a chemical conversion treatment film is suitably used for severe working such as cold forging working.

However, when end products such as bolts are manufactured by subjecting the above metal material to a heat treatment after cold wire drawing working, there is a problem that phosphorus diffuses in the metal material (phosphorus infiltration) and delayed fracture is generated during the heat treatment. Furthermore, the formation of a phosphate film requires complicate control of treatment solutions and many steps. In addition, a large amount of sludge is produced by a chemical reaction of a material to be treated (metal material) with a treatment solution, and great effort and cost are required for the disposal of the sludge.

Then, a method for forming a lubricating film having excellent lubricity and excellent seizure resistance without interposing a phosphate film has been proposed. For example, Patent Document 1 discloses a lubricant for plastic working of metallic material containing a water soluble inorganic salt (A) and a wax (B), and further a metallic salt of fatty acid (C) at the prescribed ratio. It is described that, according to this method, excellent lubricative properties can be obtained by adjusting the ratio of (B)/(A) to the range of 0.3 to 1.5 and the ratio of (C)/(A) to the range of 0.01 to 0.4.

In addition, Patent Document 2 discloses a lubricant for plastic working of metallic material containing a water soluble inorganic salt (A) and a lubricating agent (B) (molybdenum disulphide and/or graphite), and further a wax (C) at the prescribed ratio. It is described that, according to this method, excellent lubricative properties can be obtained by adjusting the ratio of (B)/(A) to the range of 1.0 to 5.0 and the ratio of (C)/(A) to be in the range of 0.1 to 1.0.

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent No. 3984159

Patent Document 2: Japanese Patent No. 3984158

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, according to the studies by the inventors, non-phosphorus lubricating films formed by the above-mentioned methods have insufficient adhesion between the lubricating film and the metal material, the lubricating film was peeled off during strong working such as cold forging and cold high strength wire drawing, and the working became difficult to be carried out. It was also founded that problems such as scattering of dust formed from the peeling lubricating film or the like have occurred. Therefore, excellent lubricity, seizure resistance and corrosion resistance, and higher adhesion have been demanded for non-phosphorus lubricating films.

The present invention was made in view of the above problems and an object of the present invention is to provide a water-soluble lubricating agent for plastic working being capable of forming a lubricating film having lubricity and seizure resistance equal to or greater than a phosphorus-containing chemical conversion treatment film, having excellent corrosion resistance, and also having good film adhesion, without containing phosphorus in the film, and a metal material for plastic working and a worked metal article provided with such a lubricating film.

Means for Solving the Problems

A water-soluble lubricating agent for plastic working according to the present invention, which can solve the problems as described above, includes an inorganic solid lubricant as component A, a wax as component B, and a water-soluble inorganic metal salt as component C, wherein mass ratio (component A/component B) of solid content for component A to solid content for component B is 0.1 to 5, and mass percentage (component C/(component A+compound B+component C)) of solid content for component C to total solid content for components A, B, and C is 1% to 30%.

According to the present invention, the inorganic solid lubricant is preferably at least one selected from the group consisting of calcium compounds, magnesium compounds, barium compounds, zinc compounds, boron compounds (in which, however, borates are not included), and silicate compounds.

Furthermore, according to the present invention, the water-soluble inorganic metal salt is preferably at least one selected from the group consisting of borates, molybdates, and tungstates.

Preferably, mass ratio (component B/component C) of solid content for the component B to solid content for the component C is higher than 1.5.

A metal material for plastic working according to the present invention, which can solve the problems as described above, includes a lubricating film on the surface thereof, wherein the lubricating film includes an inorganic solid lubricant as component A, an organic wax as component B, and a water-soluble inorganic metal salt as component C, mass ratio (component A/component B) of solid content for component A to solid content for component B is 0.1 to 5, and mass percentage (component C/(component A+component B+component C)) of solid content for component C to total solid content for components A, B, and C is 1% to 30%.

The present invention includes a worked metal article obtained by plastic working of a metal material for plastic working as described above.

Advantageous Effects of the Invention

By using the water-soluble lubricating agent for plastic working of the present invention configured as described above, a lubricating film having an excellent lubricity, excellent seizure resistance and excellent corrosion resistance as well as an excellent adhesion to a metal material can be obtained. Therefore, the lubricating agent of the present invention is suitable for strong working such as cold forging and cold high strength wire drawing and the like. Particularly, since a metal material on which the above lubricating film was formed has excellent adhesion, the metal material not only can fully cope with strong working but also can be processed without the occurrence of seizure under even severer working conditions (for example, the working without the addition of lubricating agents such as dried powders as in Example described later). Furthermore, peeling of the lubricating film accompanying working or transportation is suppressed and the occurrence of powder dust caused by the peeled-off lubricating film can be suppressed owing to low scattering property of the peeled-off film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an outline of a Bowden friction test used in the present Example;

FIG. 2 is a schematic view showing an outline of a ball passing test used in the present Example;

FIG. 3 is a schematic view showing an outline of a film adhesion test used in the present Example; and

FIG. 4 is a schematic view showing an outline of a headability test used in the present Example.

MODE FOR CARRYING OUT THE INVENTION

In order to provide a metal material for plastic working including a non-phosphorus lubricating film having lubricity, seizure resistance and corrosion resistance equal to or higher than those of a chemical conversion treatment film, the inventors studied based on particularly the lubricant as described in Patent Document 1 mentioned above [more particularly the lubricant containing a water soluble inorganic salt (C) such as sulfate that is a film forming component and a wax (B) that is a lubricant component at the ratio of (B)/(C)=0.3 to 1.5]. As a result, with regard to the example [see No. 17 in Table 1, (B)/(C)=0.3] simulating the above lubricant, the lubricity, seizure resistance, adhesion, dust resistance, wire drawability, and corrosion resistance were evaluated in the manner as described in Examples described later and it was found that any desired properties were not obtained (see No. 17 in Table 2). Then, with regard to the example significantly increasing the content ratio of wax (B) [see No. 12 in Table 1, (B)/(C)=9.0] so as to enhance the lubricity of the above lubricant, the various properties were evaluated in the same manner as above. As a result, it was found that although the adhesion was good, the seizure resistance (working under particularly severe strong working conditions) and the film strength were still poor (see No. 12 in Table 2).

Furthermore, using other lubricant [metallic salt (so-called metal soap) of fatty acid such as calcium stearate in addition to the above lubricant] described in the above Patent Document 1, the above properties were evaluated. As a result, the adhesion of the lubricating film was still low and the working could not be performed under strong working conditions or severe working conditions. Moreover, it was found that metallic salt of fatty acid such as calcium stearate (so-called metal soap) decreases the properties such as corrosion resistance since the lubricating film was damaged by metal soap scum produced during working.

Namely, it was found that the desired properties could not be obtained even if the compositions of any lubricants described in the above Patent Document 1 are used, and the lubricant having all the properties could not be obtained even if the ratios are changed.

In light of improvement of the adhesion between a metal material and a lubricating film, the inventors have conducted further intensive studies. As a result, the inventors have found that the combination in which an inorganic solid lubricant (component A) (that is different from a water-soluble inorganic salt) as a lubricating component is added to the composition (a water soluble inorganic salt as a film forming component and a wax as a lubricating component) as described in Patent Document 1 is effective and by using a water-soluble lubricating agent for plastic working in which these ratios are appropriately controlled, the desired object is achieved. Thus, the present invention has been completed.

Compared to the lubricating agent of the above Patent Document 1, the lubricating agent of the present invention is different in that an inorganic solid lubricant such as calcium compounds, magnesium compounds or the like that is not described in Patent Document 1 is used as a component of the lubricating agent in the present invention, in that a metallic salt of fatty acid is not used in the present invention while a metallic salt of fatty acid is used in Patent Document 1, and in that the preferable ratio of a wax and a water soluble inorganic metal salt used in the present invention exceeds the upper limit (1.5) of Patent Document 1.

Furthermore, the present invention is significantly different in that the excellent properties (corrosion resistance, adhesion, seizure resistance, and working under particularly severe working conditions), which the above Patent Document 1 could not achieve, can be exhibited. Actually, in the above Patent Document 1, the lubricative properties were evaluated only using a rear punching test and a spike test, the seizure resistance was not evaluated, and any properties during strong working or working under severe working conditions were not evaluated.

The components (components A to C) of the water-soluble non-phosphorus lubricating agent for plastic working according to the present invention are described below.

(1) Component A: Inorganic Solid Lubricant

The inorganic solid lubricant (component A) is a useful component that reduces the friction coefficient of a lubricating film, increases in lubricity of the lubricating film, and prevents the occurrence of seizure during plastic working. The lubricating film containing the component A with the component B has the further improved adhesion (particularly, film strength), so that the excellent effects on seizure resistance, adhesion and the like during strong working or working under severe working conditions can be exerted.

The inorganic solid lubricant is solid and yet has lubricity. Accordingly, even if the temperature of the contact portion (metal-to-metal contact) between a working tool (tools, dies or the like) and a metal material (materials to be worked) rises to about 150° C. to 400° C., the inorganic solid lubricant does not melt and the direct contact between the working tool and the metal material is prevented, whereby the occurrence of seizure during working can be prevented.

The inorganic solid lubricant used in the present invention is not particularly restricted insofar as it is an inorganic compound that is usually used as a water-soluble lubricating agent for plastic working and contains no phosphorus. Preferably, the inorganic solid lubricant stably exists in the lubricating film and has characteristics that manifest lubricity even under high load during working.

Examples of the inorganic solid lubricant include calcium compounds such as calcium hydroxide, calcium carbonate and calcium oxide (preferably, calcium salt such as calcium carbonate), magnesium compounds such as magnesium hydroxide and magnesium carbonate (preferably, magnesium salt such as magnesium carbonate), barium compounds such as barium hydroxide and barium carbonate (preferably, barium salt such as barium carbonate), boron compounds such as boron nitride (however, borate salt is excluded from the compound A), zinc compounds such as zinc oxide and zinc phosphate (preferably, zinc salt such as zinc oxide), and silicate compounds such as silicate mineral (for example, mica) (preferably silicate, however, alkali metal silicate is excluded). Of these solid lubricants, calcium compounds and zinc compounds are preferable, and calcium compounds are particularly preferable.

Any of the above-mentioned components A may be used either alone or in combination of two or more components.

Although black molybdenum disulfide and graphite are known as an inorganic solid lubricant, it is preferable not to use these compounds in view of working environment because the adherence (coloring) of these compounds to clothes or the periphery of an apparatus leads to the deterioration in working environment.

Although there is no specific restriction in the content of the component A, in order to exert the above effects of the component A, the content of the component A in all essential components (the total content of the components A, B and C) is preferably 20 mass % or more, more preferably 50 mass % or more. On the other hand, since dust properties and adhesion may deteriorate if the component A is contained too much, the content of the component A is preferably 85 mass % or less, more preferably 80 mass % or less.

(2) Component B: Wax

The wax (component B) is a useful component that reduces the friction coefficient of a lubricating film, increases in lubricity of the lubricating film, and improves seizure resistance, and also that increases in adhesion between the lubricating film and the metal material, and enhances the followability of the lubricating film during plastic working, whereby peeling of the lubricating film is prevented.

In the present invention, in view of increasing in lubricity during working, it is recommended that the wax has a property of being melted by heat by plastic working. The wax is melted by heat by plastic working whereby the friction between the working tool and the metal material can be reduced. Therefore, the melting point of the wax is preferably 50° C. or higher, more preferably 70° C. or higher and preferably 160° C. or lower, more preferably 140° C. or lower. In addition, in view of increasing in coating properties of the wax, the wax preferably has dispersibility in water (for example, dispersion or emulsion).

As the wax used in the present invention, various natural waxes and synthetic waxes can be used insofar as the wax is an organic wax that is solid at ordinary temperature and has a property of being liquefied at the prescribed temperature by heating. Examples of natural waxes include plant-based waxes such as carnauba wax, petroleum-based waxes such as paraffin wax and microcrystalline wax, animal waxes such as beeswax, and mineral waxes such as montan wax. Examples of synthetic waxes include polyethylene waxes and polypropylene waxes. In the present invention, these waxes (component B) may be used either alone or in combination of two or more waxes.

Although there is no specific restriction in the content of the component B, the content of the component B in all essential components (the total content of components A, B and C) is preferably 10 mass % or more, more preferably 20 mass % or more, and preferably 50 mass % or less, more preferably 40 mass % or less. The content of 10 mass % or more is preferable in order to exert the above effects of the component B. On the other hand, since wire drawability may deteriorate if the component B is contained too much and the content of the component A decreases, the content of the component B is preferably 50 mass % or less.

(3) Compound C: Water-Soluble Inorganic Metal Salt

The water-soluble inorganic metal salt (component C) is a film making agent (film forming agent) and a useful component that improves the adhesion to a metal material and seizure resistance. In addition, when forming a lubricating film, a film is formed from the component C so as to coat the surface of the metal material and therefore it is a useful component for improving corrosion resistance (rust-proof property).

The water-soluble inorganic metal salt of the present invention is not particularly restricted insofar as the water-soluble inorganic metal salt contains no phosphorus and is generally used as an additive of a water-soluble lubricating agent for plastic working. As examples of the water-soluble inorganic metal salt used in the present invention, borate, molybdate and tungstate can be given. The preferable water-soluble inorganic salt is borate. They may be used either alone or in combination of two or more.

Examples of boric acid forming the above borate include orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, and octaboric acid. Examples of borate include metal salts such as alkali metal salt (Li salt, Na salt, K salt or the like) and alkaline-earth metal salt (Mg salt, Ca salt or the like). The preferable borates are metaborate and tetraborate, and as specific examples, sodium metaborate, potassium metaborate, sodium tetraborate (Na₂B₄O₅(OH)₄.8H₂O called as borax), potassium tetraborate, ammonium tetraborate, and the like can be given.

The above molybdate is also useful as a rust-proofing agent. Examples of molybdic acid forming molybdate include orthomolybdic acid, metamolybdic acid and paramolybdic acid. Examples of molybdate include alkali metal salt (Li salt, Na salt, K salt or the like) and alkaline-earth metal salt (Mg salt, Ca salt or the like). The preferable molybdate is metamolybdate, and specifically, sodium metamolybdate is preferred.

Examples of tungstic acid forming the above tungstate include orthotungstic acid, metatungstic acid and paratungstic acid. Examples of tungstate include alkali metal salt (Li salt, Na salt, K salt or the like) and alkaline-earth metal salt (Mg salt, Ca salt or the like). The preferable tungstate is metatungstate and specifically, sodium metatungstate is preferred.

It is recommended that the component C of the present invention does not include alkali metal silicate as described in Patent Document 1. The fact that silicon-based substances cause coating defects (so-called cissing) is known (for example, “New engineering review of coating” 1987, p. 786). If the lubricating film of the present invention contains alkali metal silicate, the adhesion between the lubricating film and the metal material may be too high and the lubricating film cannot be sufficiently removed by washing before plating the metal material. Accordingly, the platability may degrade (plating formation obstructive factors).

The water-soluble lubricating agent for plastic working of the present invention is characterized by including the combination of the above components A, B and C, and the effects possessed by each component as described above can be exhibited effectively through the inclusion of these components at the specific ratio. The ratios of each of component are described below.

[Compounding Ratio of Component A and Component B]

When the compounding ratio of the component A (inorganic solid lubricant) and the component B (wax) (component A/component B: mass ratio of solid content, the same shall apply hereinafter) is below 0.1, the above effects of the component A are not exhibited effectively and the seizure resistance of the lubricating film decreases. Moreover, when the content of the component A is insufficient, the adhesion of the wax (component B) during working may decrease and the film may peel off easily. On the other hand, when the compounding ratio (component A/component B) excesses 5, the adhesion between the metal material and the lubricating film decreases and the followability of the lubricating film during plastic working decrease. In addition, if the adhesion or followability decreases, a sufficient dust depression effect cannot be exhibited. Therefore, the compounding ratio of the component A and the component B is 0.1 or higher, preferably 1 or higher, and 5 or lower, preferably 3 or lower.

[Ratio of Component C in the Total Content of Components A, B and C]

If the compounding ratio of the component C in the total content of the components A, B and C (component C/(component A+component B+component C): mass percentage of solid content, the same shall apply hereinafter) is below 1%, the seizure resistance or adhesion of the lubricating film decreases. On the other hand, if the compounding ratio (component C/(components A+B+C)) excesses 30%, since the lubricity decreases and the friction coefficient increases (decreasing of friction coefficient reduction effect), the seizure resistance decreases or the resistance during working increases and thus the lubricating film may peel off. In addition, when worked articles are used as bolts for example, problems such as an abnormal value of the torque coefficient may occur. Therefore, the compounding ratio of the component C in the total content of the components A to C is 1% or higher, preferably 5% or higher and 30% or lower, preferably 20% or lower.

[Compounding Ratio of Component B and Component C]

Furthermore, the compounding ratio of the component B (wax) and the component C (water-soluble inorganic metal salt) (component B/component C: mass ratio of solid content, the same shall apply hereinafter) is preferably higher than 1.5. If the ratio of component B to component C is 1.5 or lower, the balance between the adhesion and the lubricity becomes inferior, and the adhesion and the lubricity decrease and the seizure resistance of the lubricating film may decrease. On the other hand, the compounding ratio (component B/component C) excesses 9, the adhesion between the metal material and the lubricating film might decrease. Therefore, the compounding ratio of the components B and C is preferably higher than 1.5, more preferably 1.8 or higher and preferably 9 or lower, more preferably 8 or lower.

Although the water-soluble lubricating agent for plastic working of the present invention includes the above components A, B and C at the specific ratio as active constituents, other components that are usually included in a lubricating agent can be added within the scope not impairing the actions of the present invention and these are also included within the scope of the present invention.

As other components that can be included in the lubricating agent of the present invention, the following components that can be usually added in the lubricating agent used can be given.

[Surface Active Agent]

A surface active agent is a component that is added during forming process of the lubricating film, if need arises. A surface active agent is a useful component for improving dispersibility of the above component A (inorganic solid lubricant) and the above component B (wax). As described later, the above lubricating film is formed by dipping a metal material in an aqueous solution (treatment solution) containing the components as described above (a dipping method). At this time, the addition of the surface active agent allows the above component A and the above component B to be dispersed homogeneously in the treatment solution and the above effects can be exhibited more homogeneously. Moreover, since the surface active agent adsorbed on the surface of the metal material has a rust-proofing action, the corrosion resistance is also improved. Furthermore, the surface active agent ensures the homogeneous wettability on the surface of the metal material and also has the improvement action of the coating property of the lubricating film.

As examples of the surface active agent used in the present invention, a non-ionic surface active agent, anionic surface active agent, ampholytic surface active agent, cationic surface active agent and the like can be given.

Although there is no particular restriction, examples of the non-ionic surface active agent include polyoxyethylene alkyl ether, polyoxyalkylene (ethylene and/or propylene) alkylphenyl ether, polyoxyethylene alkyl ester composed of polyethylene glycol (or ethylene oxide) and higher fatty acid (having 12 to 18 carbon atoms, for example), polyoxyethylene sorbitan alkyl ester composed of sorbitan, polyethylene glycol and higher fatty acid (having 12 to 18 carbon atoms, for example) and the like. Although there is no particular restriction, examples of the non-ionic surface active agent include fatty acid salt, sulfate ester salt, sulfonate, dithiophosphoric acid ester salt, and the like. Although there is no particular restriction, examples of the ampholytic surface active agent include carboxylates either in amino acid configuration or in betaine configuration, sulfate ester salt, sulfonate, and the like. Although there is no particular restriction, examples of the cationic surface active agent include amine salt of fatty acid, quaternary ammonium salt, and the like. These surface active agents may be used either alone or in combination of two or more of them.

The content of the surface active agent contained in the lubricating agent of the present invention varies depending on the components constituting the lubricating agent or the kind of surface active agent used, and it is generally preferred that the content of the surface active agent be within the range of 0.01% to 5% relative to the basic components (the total content of the components A, B and C) constituting the lubricating agent. If the content of the surface active agent is lower than 0.01%, desired effects such as dispersibility or wettability cannot be obtained sufficiently. On the other hand, if the content of the surface active agent is higher than 5%, these actions are saturated, which just leads to the increased cost. The content of the surface active agent is preferably 0.05% or higher, more preferably 0.3% or higher and preferably 3% or lower.

[Rust-Proofing Agent]

A rust-proofing agent is a component that is added during forming process of the lubricating film, if need arises. A rust-proofing agent is a useful component for improving corrosion resistance. The kinds of the rust-proofing agent are not particularly restricted and the rust-proofing agent usually contained in a lubricating film may be used either alone or in combination of two or more. Examples of the rust-proofing agent include alkenyl succinic acid amine salt, vanadate, polyacrylic acid, benzotriazole, and the like. The content of the rust-proofing agent contained in the lubricating agent of the present invention varies depending on the components constituting the lubricating agent or the kind of the rust-proofing agent used, and it is generally preferred that the content of the rust-proofing agent be within the range of 0.1% to 5% relative to the basic components (the total content of the components A, B and C) constituting the lubricating agent. More preferably, it is 1% or higher and 4% or lower.

Next, a method for forming a lubricating film using the lubricating agent of the present invention will be explained below.

The lubricating film can be formed using the lubricating agent containing the components A to C as described above and other components that are added if need arises. Specifically, the mixture solution (sometimes referred to as a preparation solution or treatment solution) of the above components and an aqueous solvent is made to contact with the metal material and then dried if need arises, thereby forming a lubricating film (dry method). The contact method is not particularly restricted and methods usually used for forming a lubricating film using a lubricating agent can be appropriately employed. As examples of the method, a method in which the metal material is dipped in the above mixture solution and dried it, a method in which the above mixture solution is applied to the metal material (with a spray, shower or the like), or the like can be given.

The dry method used in the present invention is explained here. Methods for forming a lubricating film using an aqueous lubricating agent can be roughly classified into a wet method and a dry method. The wet method is applied in the case where a lubricating agent containing a mineral oil, an animal or plant oil, or the like as a base oil is used, and in this method the lubricating agent is poured directly on the metal material (material to be processed) to form a liquid film. This method is widely used to mainly obtain materials having a relatively low degree of processing. In contrast, in the dry method, a metal material is treated by dipping it in a lubricating agent or by doing anything, and subsequently, if need arises, water is evaporated in a drying step to form a solid film.

According to the method for forming a lubricating film in the present invention, problems such as unevenness of adhesion which are caused by the dry method can be avoided. That is, in the dry method using an aqueous lubricating agent, a large quantity of metal materials are subjected to dipping treatment at the same time and then the aqueous solvent is dried, thereby forming films. In this case, unevenness of adhesion due to partial contact with the metal materials are often generated and this leads to the problems such as seizure is likely to occur when drawing. According to the present invention, since the lubricating agent containing the above components A to C in combination at the specific ratio is used, the lubricating agent homogeneously dissolves or disperses in the treatment solution. Therefore, when the lubricating agent is made to contact with the metal material to form a lubricating film, the strong lubricating film with no film defect can be obtained. Moreover, the adhesion between the lubricating film and the metal material or the followability of the lubricating film to the metal material is significantly improved and thus the problems such as deterioration in seizure or the like caused by unevenness of adhesion as describe above are resolved. Furthermore, since water is evaporated by drying, the component composition of the lubricating agent in the film after drying can be made nearly equal to the component composition in the lubricating agent.

Hereinafter, a method for forming a lubricating film through a dipping process that is a typical example of the dry method will be explained.

First, a mixture solution is prepared by mixing the components A to C at the specific ratio described above, and in addition, if need arise, other components with an aqueous solvent.

As examples of the aqueous solvent used in the present invention, water and a mixture of water with a water-soluble solvent can be given. Examples of the water-soluble solvent include alcohol such as methanol, ethanol and ethylene glycol; ketone such as acetone; ether such as tetrahydrofuran and ethylene glycol dimethyl ether; and nitrile such as acetonitrile. The preferable aqueous solvent is water. In this case, water is ion-exchange water, tap water, groundwater, industrial water, or the like and is particularly not restricted.

The concentration of the lubricating agent when being mixed with the aqueous solvent is, generally, preferably 5% or higher, more preferably 7% or higher, and further preferably 10% or higher. If the concentration of the lubricating agent is too low, the film may be inhomogeneously formed. On the other hand, the upper limit of the concentration of the lubricating agent is not particularly restricted insofar as the lubricating agent can dissolve in the aqueous solvent, but it is, generally, preferably 70% or lower, more preferably 60% or lower. However, if the concentration of the lubricating agent is too high, the lubricating agent does not homogeneously dissolve or disperse in the aqueous solvent and thus unevenness of adhesion may be generated. In the light of the above, the concentration of the lubricating agent is, generally, preferably 50% or lower, more preferably 45% or lower.

A method for preparing a water-soluble lubricating agent for plastic working of the present invention is not particularly restricted. For example, the water-soluble lubricating agent can be prepared by adding the above component B (wax), an additive agent such as a surface active agent if need arises, and an aqueous solvent to an aqueous solution (aqueous solvent) containing the above component C (water-soluble inorganic metal salt) and stirring them, and further adding the above component A (inorganic solid lubricant) and, if need arises, an additive agent such as a surface active agent or an aqueous solvent thereto and stirring them.

Next, a metal material is dipped in the above mixture solution. The specific dipping condition is not particularly restricted, but it is generally preferred that the dipping be conducted at a temperature of about 30° C. to 80° C. (more preferably 40° C. to 70° C.) for 5 seconds or longer (more preferably 10 seconds or longer). If the dipping temperature falls below the above range, it is inconvenient to need to strictly control the dipping temperature under high-temperature environment in the summer season or the like. On the other hand, if the dipping temperature exceeds the above range, the amount of evaporation of the mixture solution may increase and thus the concentration of the lubricating agent is likely to fluctuate. In addition, if the dipping time falls below the above range, the adhesion decreases. Note that the upper limit of the dipping time is not particularly restricted, but adhesion improving action cannot be obtained by dipping for a long time and thus the dipping time is preferably for 15 minutes or shorter.

After dipping, drying may be conducted if need arises, so that the desired lubricating film can be obtained. The drying method is not particularly restricted, and natural drying, drying by hot or cold air, or drying in a greenhouse (a calm state) may be conducted after dipping.

The process for bring the metal material into contact with the mixture of the lubricating agent and the aqueous solvent (film formation process) was described in the above. However, in a previous process before the film formation process, a cleaning process may be conducted for the purpose of cleaning treatment of the surface of the metal material. As examples of the cleaning treatment, descaling, degreasing or the like can be given. As descaling, common methods such as a mechanical descaling method (a blast method such as a shot blasting, bending, or the like) or a chemical descaling method (acid-pickling or the like) can be used. The mechanical descaling method is a preferred method for descaling. By the mechanical descaling method, descaling can be conducted by in-line process not by batch process and this method is suitable for the present invention in which a film is physically formed in a short time.

The lubricating film formed by using the water-soluble lubricating agent for plastic working according to the present invention contains the components A to C in the mass ratio of solid content for components A/component B of 0.1 to 5 (the preferable mass ratio of solid content is the same as the mass ratio of solid content of the water-soluble lubricating agent for plastic working according to the present invention as described above) and in the mass percentage of solid content for component C/(components A+B+C) of 1% to 30% (the preferable mass percentage of solid content is the same as the mass percentage of solid content of the water-soluble lubricating agent for plastic working according to the present invention as described above). Note that the preferable compounding ratios of the components B and C and the preferable contents of each of the component A to C are the same as those of the above-described lubricating film. When other components are contained as an active component in addition to the above components A to C, the lubricating film contains these components at concentrations corresponding to the concentrations of other components contained in the lubricating agent.

The ratios of the components A to C (and further added other components) in the lubricating film does not completely correspond to the ratios of the composition of the water-soluble lubricating agent for plastic working used for forming the lubricating film. Depending upon methods for forming a lubricating film, the ratios within the range of about ±10% may be acceptable. Therefore, it is desirable to adjust appropriately the ratios of the components in the water-soluble lubricating agent for plastic working as necessary in such a way that the ratios of the components in the lubricating film falls within the ranges as prescribed before.

It is preferred that the adhesion amount of the above lubricating film be generally within the range of from 0.5 g/m² to 30 g/m². If the adhesion amount is less than 0.5 g/m², it is difficult to conduct a large number of continuous wire drawings because of shortage of film thickness. If the adhesion amount is more than 30 g/m², the above actions exerted by the lubricating film are saturated, and this only causes an increase in cost and is economically ineffective. More preferably, the adhesion amount of the lubricating film is generally within the range of 2 g/m² or more and 20 g/m² or less.

Even if the above lubricating film is formed directly on a metal material through no base layer, excellent properties can be exhibited (see Examples as described later). However, in order to further enhance the adhesion to the metal material and further improve the above properties, a general-purpose base layer (silica-containing layer) may be interposed between the lubricating film and the metal material.

Other films containing silica or the like may be coated on the above lubricating film in order to give rust-proof property and the like. These other films may be formed in a single layer or in two or more stacked layers.

A metal material of the present invention has the above lubricating film on the surface and is used for plastic working (the details will be described later).

The composition of the metal material used in the present invention is not particularly restricted insofar as the metal material is used for plastic working. For example, various metal materials such as steel (iron steel, stainless steel, chrome steel, molybdenum steel, titanium steel, or the like) and non-ferrous metal materials (aluminum material, titanium material or copper material or the like) are used. The preferred metal material is steel.

The configuration of the above metal material is not particularly restricted insofar as the metal material is used for plastic working. For example, various metal materials such as wire rods, rods, cutting materials of the wire rods or rods (blank materials), steel plates or the like can be used. The preferable metal materials are wire rods, rods, blank materials or the like. As examples of the wire rods and rods, the wire rods and rods for producing bolts, nuts, springs, PC (prestressed concrete) steels, steel cords, bead wires, or the like can be given. As examples of the blank material, blank materials for producing forward or backward extrusion parts can be given.

The present invention includes a worked metal article obtained by plastic working of a metal material provided with the above lubricating film. Examples of the worked metal article include bolts, nuts, springs, PC steels, steel cords, bead wires, forward or backward extrusion parts, rolled steel plates, or the like.

In the present description, “plastic working” includes cold drawing or wire drawing, heading or forging, rolling, or the like. Heading or forging includes, for example, cold heading, warm heading, or the like.

The type of plastic working can be selected appropriately depending on the application of the metal material. A plurality of plastic workings may be conducted depending on the application of the metal material. For example, when producing bolts, nuts and the like, heading is conducted after drawing. When producing forward or backward extrusion parts, wire materials or rod materials are subjected to drawing, cutting and then forging. When producing steel cords, bead wires, wire drawing is performed in a plurality of steps of a first wire drawing, a second wire drawing and so on. When conducting a plurality of plastic workings, the aforementioned lubricating film formation process may be conducted before at least one plastic working or before each plastic working.

The film adhesion amount on the surface of the worked metal article may be almost equal to the film adhesion amount on the surface of the metal material as described above, but is usually less than the film adhesion amount on the surface of the metal material and for example, preferably 0.2 g/m² or more and 20 g/m² or less (more preferably 1 g/m² or more and 15 g/m² or less).

The present application claims priority on Japanese Patent Application No. 2012-040520 filed on Feb. 27, 2012, and Japanese Patent Application No. 2013-029282 filed on Feb. 18, 2013. The contents of the descriptions of Japanese Patent Application No. 2012-040520 filed on Feb. 27, 2012 and Japanese Patent Application No. 2013-029282 filed on Feb. 18, 2013 are incorporated herein by reference in its entirety.

EXAMPLES

The present invention will be illustrated in further detail with reference to experimental examples below. It should be noted, however, that these examples are never construed to limit the scope of the present invention; and various modifications and changes may be made without departing from the scope and sprit of the present invention described hereinbefore and hereinafter and should be considered to be within the scope of the present invention. While some of the components exemplified in the context described above are used in combination in the experimental examples, the inventors have confirmed in the basic experiments that the components other than the components used in the experimental examples below have also similar effects.

Example 1 Sample

In (1) a Bowden friction test, (3) a film adhesion test and (4) a dust resistance test as described later, SPCC-SD (Steel Plate Cold Commercial-Skin pass mill Dull shinish; manufactured by Nippon Testpanel Co., Ltd; size: board thickness 0.8 mm×width 80 mm×length 100 mm) was used as a sample (metal material).

In (2) a ball passing test as described later, S10C being spherodizing annealed material (JIS G4051:2009; manufactured by Nippon Testpanel Co., Ltd.) was used as a sample. Specifically, after preparing a test piece having an inner diameter of 15 mm and a height of 50 mm, the test piece was subjected to alkaline degreasing (Daicleaner OF-222 (5% concentration) manufactured by Daido Chemical Industry Co., Ltd.; bath temperature: 60° C.; dipping time of the sample: 10 minutes). Then, after washing with water, the moisture was removed with an organic solvent (methanol) and the resulting test piece was used.

In (5) a corrosion resistance test, (6) a wire drawability test, and (7) a headability test as described later, the steel grade SCM435 (JIS G4053: 2008; manufactured by Nippon Testpanel Co., Ltd.) was subjected to hot rolling and the obtained hot rolling wire rod (diameter 12.5 mm, 860 kg) was spherodizing annealed at a temperature of 760° C., subjected to a descaling treatment by pickling (dipping in a pickling solution of 20% sulfuric acid of a temperature of 75° C. for 13 minutes and then dipping in a pickling solution of 15% hydrochloric acid of a temperature of 30° C. for 13.5 minutes), and then washed with water, and the resulting test piece was used as a sample.

[Preparing a Water-Soluble Lubricating Agent for Plastic Working]

As a lubricating film treatment solutions, the lubricating agents of Nos. 1 to 17 shown in Table 1 were prepared. The details of the components A to E in Table 1 are as follows. Industrial water was used as “water” shown in the Table.

Component a (Inorganic Solid Lubricant)

A1: calcium hydroxide

A2: calcium carbonate

A3: zinc oxide

Component B (wax)

B1: carnauba wax (the melting point of about 80° C.)

B2: polyethylene wax (the melting point of about 140° C.)

Component C (Water-Soluble Inorganic Metal Salt)

C1: sodium metaborate

C2: sodium molybdate

Other Additive Agent

D: surface active agent (sodium sulfonate)

E: rust-proofing agent (dodecenyl succinic acid amine salt)

TABLE 1 No. No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 No. 10 No. 11 Component A1 6.0 — 4.5 2.0 — — — — 1.0 — — A A2 — 6.7 — 2.0 3.5 6.5 7.2 5.7 4.0 4.0 3.0 A3 — — 1.3 0.5 0.7 — — 1.0 1.0 1.0 1.0 Component B1 3.0 2.3 — 3.0 2.3 3.0 0.9 2.3 — 2.0 2.0 B B2 — — 2.7 1.5 1.5 — 0.9 — 3.0 2.0 3.0 Component C1 1.0 — 1.5 — 1.0 0.5 1.0 0.5 1.0 1.0 — C C2 — 1.0 — 1.0 1.0 — — 0.5 — — 1.0 Component 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 D Component 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 E Water 89.8 89.8 89.8 89.8 89.8 89.8 89.8 89.8 89.8 89.8 89.8 Total 100 100 100 100 100 100 100 100 100 100 100 A/B 2.0 2.9 2.1 1.0 1.1 2.2 4.0 2.9 2.0 1.3 0.8 C/(A + B + C) 10% 10% 15% 10% 20% 5% 10% 10% 10% 10% 10% B/C 3.0 2.3 1.8 4.5 1.9 6.0 1.8 2.3 3.0 4.0 5.0 No. No. 12 No. 13 No. 14 No. 15 No. 16 No. 17 No. 18 No. 19 Component A1 — 7.7 6.7 — 8.0 — Lime Chemical A A2 — — — 4.3 — — conversion A3 — — — — — — treatment Component B1 9.0 — 3.3 0.7 — 2.5 film B B2 — 1.3 — 1.0 — — Component C1 1.0 1.0 — — 2.0 7.5 C C2 — — — 4.0 — — Component 0.1 0.1 0.1 0.1 0.1 0.1 D Component 0.1 0.1 0.1 0.1 0.1 0.1 E Water 89.8 89.8 89.8 89.8 89.8 89.8 Total 100 100 100 100 100 100 A/B — 5.9 2.0 2.5 — — C/(A + B + C) 10% 10% — 40% 20% 75% B/C 9.0 1.3 — 0.4 — 0.3 * Components A to E, Water and Total all indicate the addition amount (parts by mass).

By dipping the above samples (test pieces) in the above lubricating film treatment solution under the following conditions and subsequently drying them, the test pieces of Nos. 1 to 17 provided with each of the various lubricating films were obtained. The lubricating films were produced by the dry method, and it was confirmed in the manner of Example 2 as described later that the component compositions of the lubricating films were almost equal to the component compositions (A to E) of the lubricating agents in the lubricating film treatment solutions (see Table 3).

Specifically, in (1) the Bowden friction test, (3) the film adhesion test and (4) the dust resistance test, each test material on which a lubricating film was formed by dipping the sample in the lubricating film treatment solution (Nos. 1 to 17, 65° C.) for one minute and then naturally drying was used.

In (2) the ball passing test, each test material on which a lubricating film was formed by dipping the sample in the lubricating film treatment solution (Nos. 1 to 17, 65° C.) for one minute and then drying (temperature: 60° C., time: 30 minutes) was used.

In (5) the corrosion resistance test, (6) the wire drawability test, and (7) the headability test, each test piece on which a lubricating film was formed by dipping the sample in the lubricating film treatment solution (Nos. 1 to 17, 65° C.) for five minutes and then drying (temperature: 60° C., time: 30 minutes) was used.

As for No. 18 that is a conventional example, a lubricating film was formed on each test material under the condition of each of the above tests except that the sample was dipped in a lime lubricating agent for wire drawing (“MAC B20” manufactured by Inoue Calcium Corporation, concentration 4%, 65° C.) as a lubricating film treatment solution, and the resulting test material was used.

As for No. 19 that is a reference example, each test material on which a chemical conversion treatment film including zinc phosphate and a soap layer was formed was used. Specifically, the sample was dipped in an aqueous solution (80° C.) containing 150 g/L of a zinc phosphate chemical conversion treatment agent (“PALBOND 421X” manufactured by Nihon Parkerizing Co., Ltd.) for 7 minutes and then washed with water to form a zinc phosphate film. Subsequently, the sample was dipped in a treatment solution (80° C.) containing 70 g/L of a soap lubricating agent (“PALUBE 235” manufactured by Nihon Parkerizing Co., Ltd.) for two minutes and then dried (temperature: 90° C., time: 10 minutes) after conducting a soap treatment to form a chemical conversion treatment film.

Using each of the test materials obtained in this manner, the composition of the lubricating film was measured and also the following tests were conducted.

(1) Bowden Friction Test

The Bowden friction test is a test for evaluating seizure resistance, film adhesion and lubricity of the lubricating film. Referring to FIG. 1, the outline of the Bowden friction test is explained. Bowden friction tester manufactured by Shinko Engineering Co., Ltd. was used for the Bowden friction test.

As shown in the drawings, the Bowden friction test is a test to determine a friction coefficient μ when the test piece slides reciprocatively in the longitudinal direction of the test piece as the sliding direction with load being applied by means of a steel ball, and the number of reciprocative slidings [torsion (strain)] when the friction coefficient μ exceeds 0.1 due to film break. The larger number of slidings (sliding frequency) means that the test piece is excellent in seizure resistance, excellent film adhesion and excellent lubricity.

The detailed conditions of the test were as follows:

Temperature of test piece: 200° C.;

Load: 3 kgf;

Sliding rate: 3.7 mm/sec;

Steel ball: SUJ-2 (JIS G4805: 2008), diameter: 3/16 inches; and

Sliding length: 37 mm.

In this Example, the test pieces that the number n of reciprocative slidings (sliding frequency) exceeded 100 were evaluated as having excellent seizure resistance and excellent film adhesion. The average of the friction coefficients was measured for the purpose of reference. In this case, as for the test pieces that the number of reciprocative slidings n exceeded 100, the average of the friction coefficients when n=100 was measured, and as for the test pieces that the number of reciprocative sliding times is less than 100, the average of the friction coefficients when the films were broken was measured.

(2) Ball Passing Test

The ball passing test is a test to evaluate seizure resistance in relation to film strength (anti-film break property under high-load condition). The Bowden friction test is also for evaluating seizure resistance of the lubricating film, but is different in that seizure resistance is evaluated mainly in relation to film adhesion.

Referring to FIG. 2, the outline of the ball passing test is explained. 110 ton crank press machine manufactured by Komatsu Ltd. was used for the ball passing test.

In the ball passing test, as shown in FIG. 2, when a ball 5 (ball diameter: 21/32 inches, SUJ2) larger than the inner diameter (15 mm) of a test piece 3 placed in a die 4 was penetrated through the test piece 3 with a punch 2 (working rate: 35 spm, test temperature: room temperature), seizure resistance under the condition of a reduction of area of 8% was evaluated. The reduction of area was calculated by a reducing rate of cross-sectional areas (a projected area (that is formed of an area between the minimum inner diameter and the maximum outer diameter) in view from above of a position of 25 mm in the direction from the upper surface toward the lower surface) of the test material before and after the test (the following expression).

Reduction of area(%)=[(A−B)/(A)]×100

A: cross-sectional area of the test piece before the test

B: cross-sectional area of the test piece after the test

Seizure resistance was evaluated for seizure on the inner peripheral surface of the test piece after the test as follows. A case in which no seizure was observed was evaluated as “◯” (Excellent in seizure resistance and film strength), a case in which seizure was partly observes was evaluated as “Δ” (Slightly Poor in seizure resistance and film strength), and a case in which seizure was wholly observed was evaluated as “X” (Poor in seizure resistance and film strength). The test pieces evaluated as “◯” were judged as being acceptable.

In this Example, a case in which both of the Bowden friction test and the ball passing test satisfied the acceptability criteria (evaluation of “◯”) was evaluated as “◯” (Excellent in seizure resistance), and a case in which one or both of the Bowden friction test and the ball passing test did not satisfy the acceptability criteria was evaluated as “X” (Poor in seizure resistance) (“seizure resistance evaluation” in Table 2).

(3) Lubricating Film Adhesion Test

The adhesion test is a test for comparative evaluation of film adhesion by quantifying the adhesion between a sample and each lubricating film as shown in Table 1 as a remaining ratio (%). The film adhesion is also evaluated in the Bowden friction test, but it is different in that the film adhesion was evaluated in relation to the seizure resistance.

Referring to FIG. 3, the outline of the film adhesion test is explained. In the film adhesion test, the lubricating film was removed from only one surface of the test piece which the lubricating films were formed on the both surface, and the mass of the removed lubricating film and the mass of the test piece after removal of the lubricating film were each measured (mass before the test). Subsequently, as shown in FIG. 3, an abrasive paper 12 (#360 emery paper, 50 mm×200 mm) and a weight 13 (200 gf) were placed on a surface 11 on which the lubricating film was formed, the opposite end of the abrasive paper was pulled straight in the horizontal direction at the prescribed speed (20 mm/sec), and then the mass of the test piece was measured (mass after the test).

For the evaluation of the film adhesion test, the film remaining ratio (%) was calculated from mass difference between the test pieces before and after the test, and the test pieces having the remaining ratio of 65% or more were evaluated as being excellent in adhesion.

Note that No. 19 (chemical conversion treatment film) was a chemical reaction film and it was difficult to precisely evaluate the adhesion, and therefore the film adhesion test of No. 19 was not conducted.

(4) Dust Test

The films that were peeled off from the test pieces, which is referred to as “dropped films”, during the above lubricating film adhesion test were observed to evaluate the dust resistance. The dust resistance was evaluated as follows. A case in which dropped films that can be a factor for scattering (namely, films evaluated as “X” or “Δ”) could not almost be confirmed was evaluated as “◯”, a case in which almost no powdery dropped films were confirmed, but granular dropped films that are hard to scatter were confirmed was evaluated as “Δ”, and a case in which dropped films in fine powder form that easily scatter were confirmed was evaluated as “X”. In the present invention, “◯” and “Δ” were evaluated as being acceptable.

Note that No. 19 (chemical conversion treatment film) was a chemical reaction film and it was difficult to precisely evaluate the dust resistance, and therefore the dust test of No. 19 was not conducted.

(5) Corrosion Resistance Test

A test piece having a length of 100 mm cut out of a test material (diameter: 12.5 mm) obtained by forming a lubricity film on a sample was left in a thermo-hygrostat testing machine (“TABAI ESPEC PL-3SP” manufactured by ESPEC Corp., temperature: 40° C., humidity: 90%) for two weeks, and then the test piece was taken out and an area ratio of rust (rusting ratio) generated on the surface (39.3 cm²) of the lateral side of the test piece was calculated to evaluate the corrosion resistance.

The corrosion resistance was evaluated as follows. A case in which the area ratio of rust was 0% was evaluated as “◯” (Particularly Excellent in corrosion resistance), a case in which the area ratio of rust was more than 0% and 5% or less was evaluated as “Δ” (Excellent in corrosion resistance), and a case in which the area ratio of rust was more than 5% was evaluated as “X” (Poor in corrosion resistance). In the present invention, the area ratio of rust of 5% or less were evaluated as being acceptable.

Next, in order to evaluate the properties of the lubricating film during the production process of actual products, (6) a wire drawability test and a (7) headability test were conducted under the following conditions.

(6) Wire Drawability Test

Each test material (diameter: 12.5 mm, 860 kg) was subjected to a wire drawing by means of a single die until the diameter reached 10.85 mm (reduction of area: 24.7%). In this case, a dried powder lubricating agent was not used. The drawing rate of the wire drawing was adjusted to 53 m/min using a single block drawing machine. Note that although in a usual wire drawing process, a dried powder lubricating agent is added to reduce friction resistance (seizure resistance) between a workpiece and a wire drawing machine, it has been pointed out that scattering of the dried powder lubricating agent due to vibration or the like of the machine during working is one of factors deteriorating a working environment. If the dried powder lubricating agent is not used, such a problem does not occur, but the decrease in lubricity during working leads to the occurrence of seizure, and as a result it becomes difficult to conduct the wire drawing. Therefore, it has been conventionally necessary to use the dried powder lubricating agent (or other lubricating agents) during the wire drawing. In this Example, the wire drawability test was conducted under the severe conditions without using the dried powder lubricating agent.

The surface state (surface skin) of each of the test materials when conducting the wire drawing was observed. The test material that could be drawn without the occurrence of seizure on the surface was evaluated as being excellent in seizure resistance (“◯” in the table). Note that the wire drawing was stopped once the seizure occurred on the surface (“X”: in the table). The results are shown in Table 2.

(7) Headability Test

The heading is extrusion to be conducted in order to work the materials after wire drawing into a shape of a product. The headability was evaluated by the presence or absence of the occurrence of seizure when the test materials after wire drawing were worked by heading. Specifically, the above test materials after wire drawing were cut into 23.1 g/piece to produce 1000 cut pieces (test pieces: diameter: about 10.85 mm, length: about 31.9 mm) and subsequently the test pieces were subjected to forward extrusion with a heading machine. At this time, the heading was performed in two steps as shown in FIG. 4, and the shaft was reduced at the reduction of area of 50% to produce a worked article. The headability was evaluated as follows. A case in which no seizure occurred was evaluated as “◯”, a case in which the test pieces having slight seizure were generated but all the test pieces could be worked was evaluated as “Δ”, and a case in which seizure fully occurred and all the test pieces could not be worked was evaluated as “X”. In the present invention, the cases of “◯” were evaluated as being acceptable.

As for Nos. 12 to 18 in which seizure was occurred in the above evaluation of wire drawability and the prescribed wire drawing could not be conducted, the headability was not evaluated.

TABLE 2 Evaluated Test mehod item No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 (1)Bowden Average of    0.048    0.045    0.046    0.043    0.044    0.045    0.056 test friction Number of 100< 100< 100< 100< 100< 100< 100< sliding n (2)Ball Load (KN) 82 87 77 78 75 83 88 passing test Seize ◯ ◯ ◯ ◯ ◯ ◯ ◯ resistance (3)Adhesion Reduction of 82% 77% 80% 88% 87% 84% 69% area (%) (4)Dust Evaluation ◯ Δ ◯ ◯ ◯ ◯ Δ resistance (5)Corrosion Rusting  0%  3%  0%  0%  0%  3%  3% resistance ratio (6)Drawability Seize ◯ ◯ ◯ ◯ ◯ ◯ ◯ resistance (7)Headability Seize ◯ ◯ ◯ ◯ ◯ ◯ ◯ resistance Seize resistance evaluation ◯ ◯ ◯ ◯ ◯ ◯ ◯ Comprehensive evaluation ◯ ◯ ◯ ◯ ◯ ◯ ◯ Evaluated Test mehod item No. 8 No. 9 No. 10 No. 11 No. 12 No. 13 No. 14 (1)Bowden Average of    0.053    0.046    0.044    0.042    0.051    0.067    0.048 test friction Number of 100< 100< 100< 100< 100< 70 100< sliding n (2)Ball Load (KN) 83 81 78 74 118  153  141  passing test Seize ◯ ◯ ◯ ◯ x x x resistance (3)Adhesion Reduction of 75% 72% 86% 92% 97% 58% 73% area (%) (4)Dust Evaluation Δ ◯ ◯ ◯ ◯ x ◯ resistance (5)Corrosion Rusting  0%  0%  0%  0% 10%  0% 30% resistance ratio (6)Drawability Seize ◯ ◯ ◯ ◯ x x x resistance (7)Headability Seize ◯ ◯ ◯ ◯ — — — resistance Seize resistance evaluation ◯ ◯ ◯ ◯ x x x Comprehensive evaluation ◯ ◯ ◯ ◯ x x x Evaluated Test mehod item No. 15 No. 16 No. 17 No. 18 No. 19 (1)Bowden Average of    0.074    0.073    0.074    0.087    0.042 test friction Number of 70 60 54 40 60 sliding n (2)Ball Load (KN) 89 158  166  172  80 passing test Seize ◯ x x x ◯ resistance (3)Adhesion Reduction of 83% 48% 56% 51% — area (%) (4)Dust Evaluation ◯ x x x — resistance (5)Corrosion Rusting  0%  0% 18% 90%  3% resistance ratio (6)Drawability Seize x x x x ◯ resistance (7)Headability Seize — — — — ◯ resistance Seize resistance evaluation x x x x x Comprehensive evaluation x x x x Δ

The following can be considered from Table 2.

Each of Nos. 1 to 11 is an example in which the lubricating film using the lubricating agent satisfying the requirements of the present invention is formed, has good results in any tests of the above (1) to (7), and is superior to No. 18 (lime film) in seizure resistance, lubricity, adhesion (dust resistance), and corrosion resistance. In addition, these are also superior to No. 19 (chemical conversion treatment film) in seizure resistance. Particularly, Nos. 1 to 11 were better in adhesion between the lubricating film and the metal material as compared with the conventional example, and therefore even if not using a dried powder lubricating agent in the wire drawing test, the wire drawing could be carried out without the occurrence of seizure, the excellent seizure resistance was exhibited and the working environment could be also improved because the wire drawing could be conducted without using dried powder.

In contrast, the below examples unsatisfying any of the requirements of the present invention have the following defects.

No. 12 is an example in which the lubricating agent containing the component B (wax) and the component C (water-soluble inorganic metal salt) was used (it is an example in which the component A (inorganic solid lubricant) was not contained and the content ratio of the wax of the above Patent document 1 was increased). The results of (1) the Bowden friction test and (3) the adhesion test of No. 12 were good and it is considered that this is due to the addition of a large amount of wax (B1) having a relatively high adhesion. Since this lubricating film did not contain the component A, the film strength under a high load was low and thus the seizure resistance was poor in (2) the ball passing test. Since No. 12 did not contain the component A that improves the adhesion in spite of using the wax (B1) with a low melting point, the lubricating film was peeled off and the seizure occurred when the processing heat produced by friction exceeded the melting point of the wax in (6) the wire drawability test under the severe processing conditions and accordingly No. 12 could not be processed.

No. 13 is an example in which the lubricating agent containing the component A (inorganic solid lubricant), the component B (wax) and the component C (water-soluble inorganic metal salt) was used, and in which the content ratio for the component A is high and the ratio of the component A to the component B (component A/component B=5.9) is higher than the prescribed ratio in the present invention. No. 13 had the same effect as Nos. 1 to 11 with regard to only the corrosion resistance, but seizure resistance, adhesion, lubricity, and dust resistance were poor.

No. 14 is an example in which the lubricating agent containing the component A (inorganic solid lubricant) and the component B (wax) was used (the component C (water-soluble inorganic metal salt) being not contained). Since the wax (B1) having a relatively high adhesion was used in No. 14, the results of (1) the Bowden friction test and (3) the adhesion test were good. However, since the component C was not contained, the result of (5) the corrosion resistance was poor. The film strength under a high load was low and thus the seizure resistance was poor in (2) the ball passing test. In addition, since the low melting point of the wax (B1) is low and the component C was not contained, the lubricating film was peeled off and seizure occurred during the wire drawability test (6) under the severe working conditions, and accordingly No. 14 could not be processed.

No. 15 is an example in which the lubricating agent containing the component A (inorganic solid lubricant), the component B (wax), and the component C (water-soluble inorganic metal salt) was used. This is the example in which the content ratio of the component C is high and the mass percentage of the component C to the total content for the components A to C (C/(A+B+C)=40%) is higher than the percentage prescribed in the present invention. Since the percentage of the components A and B of No. 15 meets the percentage prescribed in the present invention, the film adhesion was good. The corrosion resistance was also good due to the high content of the component C, but the seizure resistance was poor in (1) the Bowden friction test because of the too high content ratio of the component C, and the seizure occurred during (6) the wire drawability test under the severe processing conditions, and accordingly No. 15 could not be processed by wire drawing.

No. 16 is an example in which the lubricating agent containing the component A (inorganic solid lubricant) and the component C (water-soluble inorganic metal salt) was used (the component B (wax) being not contained). Since No. 16 did not contain the component B, the seizure resistance, adhesion (dust resistance), and lubricity were poor.

No. 17 is an example in which the lubricating agent containing the component B (wax) and the component C (water-soluble inorganic metal salt) was used (the component A (inorganic solid lubricant) being not contained), and it is an example simulating the above Patent Document 1. The seizure resistance, adhesion (dust resistance), lubricity, and corrosion resistance of No. 17 were poor. It is considered that the lubricating film had the low adhesion because of not containing the component A, and this led to the state where the lubricating film was floating, and the corrosion resistance and the like deteriorated. In addition, since the component A was not contained, the lubricating film was peeled off and the seizure occurred during (6) the wire drawability test under the severe working conditions, and accordingly No. 17 could not be processed.

No. 18 is a conventional example (a lime film) and the adhesion of the film itself is low and therefore any of the test results of the above (1) to (7) were poor and the adhesion, seizure resistance, lubricity and corrosion resistance were poor. Particularly during (6) the wire drawability test, the lubricating film was peeled off when introducing the test material to the die and since the sufficient lubricating film did not remained at the time of wire drawing, the seizure occurred, and accordingly No. 18 could not be processed.

No. 19 is a reference example using a chemical conversion treatment film and mostly showed good results even though the result of (1) the Bowden friction test was poor.

(Comprehensive Evaluation)

Based on each test in the Example described above, the lubricating films of Nos. 1 to 17 were evaluated.

The criteria for evaluation are as follows.

“◯”: (1) the Bowden test evaluation: the average friction coefficient of 0.06 or less and the number of slidings of more than 100; (2) the ball passing test: the seizure resistance evaluation of “◯”; (3) the adhesion: the remaining ratio of 65% or more; (4) the dust resistance: the evaluation of “Δ” or better; (5) the corrosion resistance: the area ratios of rust of 5% or less; (6) the wire drawability: the evaluation of “◯”; and (7) the headability: the evaluation of “◯”. “Δ”: In the above tests, a case in which even one item did not meet the evaluation criterion of “◯” was evaluated as “Δ”. However, a case in which at least one of (6) the wire drawability and (7) the headability was “X” was evaluated as “X”. “X”: In the above tests, a case in which two or more items did not meet the evaluation criteria of “◯” (except not evaluated items) was evaluated as “X”.

As shown in Table 2, Nos. 1 to 11 formed from the lubricating agent containing the components A to C at the specific ratio exhibited excellent properties in any of the tests (the comprehensive evaluation: “◯”. Nos. 1 to 11 have the superior properties to No. 18 (lime film), and further exhibited the similar properties as compared with No. 19 (chemical conversion treatment film) in (2) the ball passing test, (5) the corrosion resistance test, (6) the wire drawability test and (7) the headability test, and also have the superior property to No. 19 in (1) the Bowden friction test.

On the other hand, the lubricating films of Nos. 12 to 17 could not meet the evaluation criteria (the comprehensive evaluation: “X” and particularly, any of the test materials could not be worked due to the occurrence of seizure in (6) the wire drawability test.

Example 2

As for the test materials Nos. 1 to 11 provided with each of the various lubricating films obtained by dipping a sample (test piece) in each of the lubricating film treatment solutions of Nos. 1 to 11 in Table 1 and subsequently drying, the components in the lubricating film formed on each of the test material were examined in the manner describe below.

The sample (SCM435: diameter: 12.5 mm, length: 200 mm) was dipped in the lubricating film treatment solution (Nos. 1 to 11) as shown in Table 1 for one minute and subsequently dried (temperature: 60° C., time: 30 minutes), to prepare each five of the test materials on which the lubricating film was formed. The mass of each test materials on which the lubricating film was formed was measured and subsequently the test materials were washed with a cleaning solution (distilled water) to completely remove the lubricating films. The mass of each test material that the lubricating film had been removed was measured and the lubricating film adhesion amount was calculated from the mass difference (the mass of five test materials) between the test materials before and after washing (“lubricating film adhesion amount (g)” in Table 3).

(1) Measurement of the Content of Component C (Water-Soluble Inorganic Metal Salt) (“Filtered Substance 4 (Component C)” of the Column of “Measurement Value” in Table 3)

The cleaning solution containing the lubricating film removed from the above test materials was filtered with a membrane filter (pore diameter: 0.45 μm). The filtrate obtained by filtering was dried to remove water and the mass of the remaining filtered substance (the substance that had passed through the filter) was measured (“Filtered substance 1” of the column of “Measured value” in Table 3). Note that the filtered substance 1 contains the component C (water-soluble inorganic metal salt), the component D (surface active agent), and the component E (rust-proofing agent), and the mass of the component C (filtered substance 4) was calculated based on the addition percentage of the components C to E added to the lubricating film treatment solution in the following manner.

Mass (g) of component C (filtered substance 4)=mass (g) of filtered substance 1×addition percentage (%) of the components C+(addition percentage (%) of components C+addition percentage (%) of components D+addition percentage (%) of components E)

(2) Measurement of the Content of Component A (Inorganic Solid Lubricant) (“Filtered Substance 2 (Component A)” of the Column of “Measured Value” in Table 3)

The residue collected on the filter after filtering in the above (1) was dried to remove water, and then the remaining filtered substance (the substance that had not passed through the filter) together with the filter was added to a container containing a mineral oil (“Super Oil M46” manufactured by JX Nippon Oil & Energy Corporation, 200 ml) heated to 190° C. and dipped for five minutes, and subsequently was filtered with a membrane filter (pore diameter: 0.45 μm) without being cooled. A mineral oil (190° C.) was further supplied to the membrane filter so as to be washed sufficiently. After being cooled to a room temperature, the residue on the filter was sufficiently washed with diethyl ether, and then dried to remove water and diethyl ether, and the mass of the remaining filtered substance was measured (filtered substance 2 (component A)).

(3) Measurement of the Content of Component B (Wax) (“Filtered Substance 3 (Component B) (g)” of the Column of “Measured Value” in Table 3)

The filtrate after being washed with the mineral oil and diethyl ether (room temperature; the filtrate containing the mineral oil and diethyl ether) in the above (2) was filtered with a membrane filter (pore diameter: 0.45 μm), the residue collected on the filter was sufficiently washed with diethyl ether, and then dried to remove water and diethyl ether, and the mass of the remaining filtered substance (the substance that had not passed through the filter) was measured (filtered substance 3 (component B)).

The measurement results are shown in Table 3.

TABLE 3 No. No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 No. 9 No. 10 No. 11 Lubricating film adhesion amount (g) 0.0762 0.0842 0.0901 0.0822 0.0941 0.0911 0.0980 0.0802 0.0871 0.0782 0.0703 Theoretical Filtered substance 1 (g) 0.0090 0.0099 0.0150 0.0097 0.0203 0.0063 0.0115 0.0094 0.0102 0.0092 0.0083 value Filtered substanc 2 0.0448 0.0553 0.0512 0.0363 0.0387 0.0581 0.0692 0.0527 0.0512 0.0383 0.0276 (component A) (g) Filtered substance 3 0.0224 0.0190 0.0239 0.0363 0.0351 0.0268 0.0173 0.0181 0.0256 0.0307 0.0345 (component B) (g) Filtered substance 4 0.0075 0.0083 0.0133 0.0081 0.0185 0.0045 0.0096 0.0079 0.0085 0.0077 0.0069 (component C) (g) Measured Filtered substance 1 (g) 0.0085 0.0094 0.0145 0.0096 0.0199 0.0063 0.0106 0.0104 0.0100 0.0089 0.0076 value Filtered substanc 2 0.0468 0.0577 0.0531 0.0381 0.0404 0.0610 0.0711 0.0544 0.0529 0.0408 0.0302 (component A) (g) Filtered substance 3 0.0219 0.0186 0.0246 0.0365 0.0352 0.0266 0.0162 0.0175 0.0252 0.0320 0.0339 (component B) (g) Filtered substance 4 0.0071 0.0078 0.0128 0.0080 0.0181 0.0045 0.0088 0.0087 0.0083 0.0074 0.0063 (component C) (g) Total of 0.0772 0.0857 0.0922 0.0842 0.0955 0.0939 0.0979 0.0823 0.0881 0.0817 0.0717 Filtered substances 1 to 3 (g) A/B 2.1 3.1 2.2 1.0 1.1 2.3 4.4 3.1 2.1 1.3 0.9 C/(A + B + C) (%) 9.4 9.3 14.1 9.7 19.3 4.9 9.2 10.8 9.6 9.2 8.9 B/C 3.1 2.4 1.9 4.6 1.9 5.9 1.8 2.0 3.0 4.3 5.4

In Table 3, the theoretical value is a value that the content for each component was calculated based on the content ratio of the components A to E contained in the lubricating film treatment solution as shown in Table 1 from the above-described lubricating film adhesion amount.

Compared the theoretical value to the measured value, the content of each component contained in the lubricating film showed approximate values within ±10% of the theoretical values (including measurement errors). Moreover, the ratios ([A/B], [C/(A+B+C)], [B/C]) of the components A to C in the lubricating film also showed approximate values to the ratios of the components A to C in each lubricating film treatment solution as shown in Table 1.

Therefore, it was found that the lubricating film having a component composition approximately corresponding to the component composition in the lubricating film treatment solution could be formed on the metal material by appropriately adjusting the component composition in the lubricating film treatment solution.

EXPLANATION OF REFERENCE NUMERALS

-   1 Load cell -   2 Punch -   3 Test piece -   4 Die -   5 Ball -   11 Test piece (the surface on which the lubricating film was formed) -   12 Abrasive paper -   13 Weight 

1. A water-soluble non-phosphorus lubricating agent for plastic working, comprising: an inorganic solid lubricant as component A; a wax as component B; and a water-soluble inorganic metal salt as component C; wherein mass ratio (component A/component B) of solid content for component A to solid content for component B is 0.1 to 5, and mass percentage (component C/(component A+compound B+component C)) of solid content for component C to total solid content for components A, B, and C is 1% to 30%.
 2. The water-soluble non-phosphorus lubricating agent for plastic working according to claim 1, wherein the inorganic solid lubricant is at least one selected from the group consisting of calcium compounds, magnesium compounds, barium compounds, zinc compounds, boron compounds (in which, however, borates are not included), and silicate compounds.
 3. The water-soluble non-phosphorus lubricating agent for plastic working according to claim 1, wherein the water-soluble inorganic metal salt is at least one selected from the group consisting of borates, molybdates, and tungstates.
 4. The water-soluble non-phosphorus lubricating agent for plastic working according to any of claims 1 to 3, wherein mass ratio (component B/component C) of solid content for the component B to solid content for the component C is higher than 1.5.
 5. A metal material for plastic working, comprising a lubricating film on the surface thereof, wherein: the lubricating film comprises an inorganic solid lubricant as component A, an organic wax as component B, and a water-soluble inorganic metal salt as component C; mass ratio (component A/component B) of solid content for component A to solid content for component B is 0.1 to 5; and mass percentage (component C/(component A+component B+component C)) of solid content for component C to total solid content for components A, B, and C is 1% to 30%.
 6. A worked metal article obtained by plastic working of the metal material for plastic working as set forth in claim
 5. 